The present invention relates to a method for the quantitative determination of a specific component in a sample using an enzyme reaction. The method of the present invention is useful in clinical assays.
When quantitatively determining a specific component in a biological sample using an enzyme reaction, galactose present in the sample often disturbs accurate determination of the specific component. In such cases, prior to the quantitative determination, galactose is preferably first decomposed or converted into a substance which does not disturb the determination.
Previous methods for decomposing or converting galactose in samples include methods in which galactose is separated by ion exchange column chromatography disclosed in EP-A-261591 (U.S. Pat. No. 4,994,377) and Japanese Published Unexamined Patent Application No. 6756/89. However, these column chromatographic methods involve complicated procedures, and are unsuitable for clinical assays.
The level of 1,5-anhydroglucitol in human samples is known as a diagnostic marker for diabetes. EP-A-213279 (U.S. Pat. No. 4,810,640) discloses a method for quantitatively determining 1,5-anhydroglucitol which comprises: (1) reacting 1,5-anhydroglucitol in a sample with oxidase, and (2) determining the amount of the oxygen consumed, the hydrogen peroxide formed, or the reductant of an electron acceptor formed as a result of the oxidase reaction. However, oxidases using 1,5-anhydroglucitol as substrate have low substrate specificity, and they also react with galactose in the samples. Therefore, it is undesirable to apply these methods to samples containing a large amount of galactose.